The invention relates to a heald loom and to a method for regulating a heald loom.
Known heald looms comprise a weaving machine for the insertion of a west thread and a dobby as an apparatus for the formation of the shed. The weaving machine and the dobby can usually be coupled to one another via a transmission apparatus, for example via a clutch and a gear box, and have a common drive train in the coupled state. This common drive train is usually driven by means of a drive--usually a motor--and in turn drives both the weaving machine and the dobby.
Heald looms of this kind have the disadvantage that a motor with a high power output is required (e.g. as a result of a large number of heavy heald frames or a large web width), in particular when driving a large dobby. Furthermore, the torque required both by the weaving machine and by the dobby in the free-running state varies in dependence on the angle of rotation (instantaneous rotary position). This is caused above all by various massive oscillating components of the individual machines. As the size of the dobby and the speed of rotation of the weaving machine increase, the load to which the entire drive train is subjected, in particular also part of the drive train arranged between the weaving machine and the dobby, increases considerably. In addition, the required torque also depends on other operating parameters, such as, e.g., the speed of rotation, the type of cloth or the weaving pattern to be produced.
The torques that arise when the machine starts up and torque fluctuations produced as a result of fluctuations in the speed of rotation can exceed the power capacity of the motor and/or the permissible load on the drive train, or at least considerably shorten its lifetime. It is then not only necessary to provide a high-power motor, the entire drive train must also be strengthened, requiring stronger shafts, transmissions, clutches, bearings, etc., which represents a considerable technical cost and effort and makes the machine significantly more expensive.
In the field of Jacquard weaving machines EP-A-0 736 622 discloses to provide an auxiliary motor for the Jacquard attachment which is independent of the drive of the weaving machine, and to couple the drive shaft of the weaving machine to the drive shaft of the Jacquard apparatus via a synchronization shaft. The drive shaft of the Jacquard attachment can be additionally driven by means of this auxiliary motor. The auxiliary motor thus serves--when appropriately actuated--for the relief of the drive of the weaving machine as well as for the relief of the entire drive train. At the same time the synchronization shaft provides for a more or less adequate synchronization of the weaving machine and the Jacquard apparatus. In order to determine now which torque must be supplied by the auxiliary motor for the relief of the drive of the weaving machine, or for the relief of the drive train, an angle sensor is provided which detects the current rotary position of the drive shaft of the Jacquard attachment and supplies it to a control system. The control system then determines, with knowledge of the desired weaving pattern and the torques required at the respective angle of rotation (the required torques must thus already be known to the control system for each angle of rotation prior to starting the machine), the torque to be supplied by the auxiliary motor in order to relieve the drive of the weaving machine as well as the entire drive train.
The Jacquard weaving machine described in EP-A-0 736 622 is theoretically capable of functioning, but the proposed procedure is not simple to apply for heald looms, especially for large heald looms with heavy heald frames. As a result of the torque fluctuations produced by large oscillating masses and by fluctuations in the speed of rotation and other operating parameters, the relationship between the actual torque present along the drive shaft and the respective peripheral position of the drive shaft of the dobby, in particular in large heald looms, is namely not constant and therefore also cannot be predicted, or at best can only be imprecisely predicted. An exact prediction of the torque arising along the drive train in dependence on the respective peripheral position is in any case not possible in practice. Therefore very large torques can still arise along the drive train, in particular in the part of the drive train arranged between the dobby and the weaving machine. Thus in order to ensure a high degree of reliability and/or availability of the machine, similarly elaborate measures with respect to the dimensioning of the drives and the drive train as described above must be taken.
Furthermore, a heald loom is disclosed by EP-A-0 743 383 which operates in accordance with a principle similar to that of the Jacquard weaving machine already explained above. In this machine a main motor is also provided for driving the weaving machine and is coupled via a mechanical transmission apparatus to a dobby (or, alternatively, to a Jacquard attachment). Furthermore, an auxiliary motor is provided at the dobby which relieves the main motor and/or the drive train. The type of control of the main motor presupposes that the torque required for the driving of the dobby at a definite speed of rotation is known to the control system prior to starting up the machine for every angle of rotation (rotary position), whether it be through a "theoretical" determination of the required torque performed prior to the start, or through values for the torque determined in trial runs. In practice, however, as a result of the torque fluctuations produced by the large oscillating masses, in particular in large dobbies with heavy heald frames, and as a result of the torque fluctuations produced by speed of rotation fluctuations and other operating parameters, the torque actually present along the drive train cannot be or at best can be only very imprecisely predicted in dependence on the rotary position. Large torques can still arise in the part of the drive train arranged between the weaving machine and the dobby in particular. Therefore, in order to ensure a high degree of reliability and availability of the machine, correspondingly elaborate measures with respect to the dimensioning of the drives and of the drive train must be taken as described above.